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Thread: Which Twist Rate

  1. #71
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    Quote Originally Posted by Belmont31R View Post
    Federal makes a GMM in both 69, and 77 grain. If he is using 69 grain it may stabilize in a Colt 1x9 barrel.
    Fed 69 SMK: I have shot these out of other 1/9 rifles (Bushmasters and RRAs) without any problems. In fact they all shot very tight groups. Based on my experience, I have complete confidence these rounds are very effective when shooting center mass or taking a more precision head shot. Not including my DAEWOO which I picked up new in the 80's and the 6721 all my rifles are 1/7 twist. I will say the Colt Tactical which I have made NO modifications to is a favorite. I like it just the way it is right out of the box 1/9.......Keep in mind some of us have to worry about over penetration in the environment in which we work.
    Last edited by lt211; 06-09-10 at 08:12.

  2. #72
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    Quote Originally Posted by az doug View Post
    If we follow the logic of the 1X8 twist for the "maximum velocity," wouldn't a 1X9 push 55 to 62 grain bullets a little faster than a 1X8 or 7? (To me it is a rhetorical question)

    Many agencies issue cartridges with 55 grain projectiles and that is all their officers are going to shoot. Applying the logic of the slower twist rate equaling more velocity, then you are increasing the distance you can get effective fragmentation/terminal ballistics from a 55 grain bullet with a 1X9 twist barrel. Some I know still use 1X12 twist barrels. They are M-16A1's on lend/lease from the Federal Government.

    I personally do not think the 1X9 twist is totally useless in the law enforcement community as long as agencies are issuing ammunition in 55 to 62 grain range.

    I am certain I will get flamed for this, but it won't be the first time. I personally use 1X8 for competition and 1X7 for defense also, but I do not believe 1X9 is useless, just less desirable to me.
    1x9 barrels will push 55-62gr a little faster than 1x7 as a whole, I've noticed typically 20-30fps with 16" barrels. But then again I've seen the same difference between to identical 1x7 16" barrels shooting the same loads. It's not as noticeable as it is with 1x8 vs. 1x7 with 75-77gr ammo. The heavier the bullet the more the momentum and thus the better velocity. 90% of the time if you chrono two 16" barrels 1x7 vs 1x8 you'll see that the 1x8 pushes 75-77gr ammo consistently faster than the 1x7. Usually I see a 30-50fps increase using the 1x8. And this is why I prefer a 1x8 for my 3gun rifle, for matches where I'll be doing a lot of shooting past 200yds I use Prvi 75gr MATCH ammo, if it's mostly inside 200yds I use various 55gr stuff but typically blue box Black Hills .

    As stated earlier 1x9 is useless to me, it offers nothing to me that 1x7 or 1x8 can't do and if I accidentily mounted a suppressor on a 1x9 barrel and had a mag loaded with 75gr or 77gr ammo I could ruin my day and F'up a nice suppressor. I've owned 1x9 barrels and yes they work fine for 45-69gr ammo....I've since sold or shot out and or disposed of those barrels.
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  3. #73
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    Quote Originally Posted by vicious_cb View Post
    Id like to know how much twist rate affects velocity granted every other aspect of the barrels are equal.
    For .223/5.56mm and 1:7" twist versus 1:9" twist it doesn't. There is no statistically significant difference in velocity between a 1:9" twist barrel and a 1:7" twist barrel of identical construction. I've chronographed more than 40 different AR-15 barrels and any difference in velocity between a 1:9" twist and a 1:7" twist is simply due to barrel to barrel variations; not the twist. You'll see as much variation between two identical barrels with the same twist as you will between otherwise identical barrels with a 1:7" twist versus a 1:9" twist.

    Anyone claiming a generalized significant increase in velocity with a 1:9" twist over a 1:7" twist doesn't have the facts behind them and I challenge anyone making such a claim to post statistically significant data supporting their claim.
    Last edited by Molon; 06-10-10 at 00:35.
    All that is necessary for trolls to flourish, is for good men to do nothing.

  4. #74
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    Quote Originally Posted by gotm4 View Post
    But then again I've seen the same difference between to identical 1x7 16" barrels shooting the same loads. It's not as noticeable as it is with 1x8 vs. 1x7 with 75-77gr ammo. The heavier the bullet the more the momentum and thus the better velocity. 90% of the time if you chrono two 16" barrels 1x7 vs 1x8 you'll see that the 1x8 pushes 75-77gr ammo consistently faster than the 1x7. Usually I see a 30-50fps increase using the 1x8. And this is why I prefer a 1x8 for my 3gun rifle, for matches where I'll be doing a lot of shooting past 200yds I use Prvi 75gr MATCH ammo, if it's mostly inside 200yds I use various 55gr stuff but typically blue box Black Hills .

    ...[snip]...
    Interesting info, I own rifles in both 1/8 and 1/7, and have often wondered about the real-world differences between the two.

    Aside from this velocity difference, are there any other practical differences between 1/7 and 1/8 that would lead you to pick one over the other for certain applications?

  5. #75
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    Quote Originally Posted by bkb0000 View Post
    1/9 is nothing more than less capable.. and reduced capability is gay.
    Indeed.

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    I'm done with the whole argument thing, but I do have a few questions.

    What would happen if you would fire 77GR ammo out of a 1:9 unsuppressed barrel? I know it will start to tumble, but how soon does that happen? Right at the muzzle, 5ft, 10ft, 25yds? Will it damage the weapon? Is it unsafe to even try?

    Now if the bullet does start to tumble right out of the muzzle, how does that effect accuracy? Will it throw it way off, would it only be a couple MOA? If it only throws it off say 6" at a 100yds, then that would in theory only equate to maybe less than an inch at 10ft. Would that not tend to do more damage to the bad guy? In turn equating to more stopping power.

  7. #77
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    Quote Originally Posted by Fyrhazzrd View Post
    I'm done with the whole argument thing, but I do have a few questions.

    What would happen if you would fire 77GR ammo out of a 1:9 unsuppressed barrel? I know it will start to tumble, but how soon does that happen?
    Generally speaking, you wouldn't notice a huge difference inside 100 yards. Outside of that, the bullet will get wild in a hurry.

  8. #78
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    Quote Originally Posted by Fyrhazzrd View Post
    I'm done with the whole argument thing, but I do have a few questions.

    What would happen if you would fire 77GR ammo out of a 1:9 unsuppressed barrel? I know it will start to tumble, but how soon does that happen? Right at the muzzle, 5ft, 10ft, 25yds? Will it damage the weapon? Is it unsafe to even try?

    Now if the bullet does start to tumble right out of the muzzle, how does that effect accuracy? Will it throw it way off, would it only be a couple MOA? If it only throws it off say 6" at a 100yds, then that would in theory only equate to maybe less than an inch at 10ft. Would that not tend to do more damage to the bad guy? In turn equating to more stopping power.
    You just have to test it at various ranges to see if your 1 in 9" is on the cusp on stabilizing the bullet. The bullet won't tumble per se, but it will yaw or wobble some. Think of an ugly football pass where there's no tight, stable spiral.

    This isn't an exact science, actual rifling twist may be a bit quicker and some a bit slower than 1 in 9. You'll be able to see keyholing on the target as stability falls below the threshold, and prior to that groups will open up.

    If relegated to a 1 in 9 barrel, I'd drop down in bullet weight (68-69 OTM or something lighter) rather than shoot 75 OTM that's on the cusp of stability. That's just MHO.

  9. #79
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    You also have to consider environmental issues. Temperature, humidity, altitude, and so on. Something that shoots well on a warm dry day at sea level may not preform so well if shot in the cold mountain air.

  10. #80
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    Apparently you want to argue for the sake of arguing just as many do when they find out they made an un-informed decision. GotM4 and the others are trying to make you realize that with a 1/7 barrel you can shoot a wide range of projectiles up to at least 77gr. These rounds are proving to be more effective.

    With a 1/9 you are limited as to what type of defensive rounds you can use. We at M4Carbine.net take issues of self defense more seriously than other well known websites.

    So yes, unless you are just going to punch paper or dirt they are essentially worthless.

    Please tell us what weapon you are referring to that the U.S military used that had a 1/11 twist? It surely wasn't the M16 because as far as I know they were either 1/12 or 1/14.

    Quote Originally Posted by Fyrhazzrd View Post
    No they are just claiming that a 1x9 is completely useless for shooting anything other than dirt. So that implies that it will not kill someone. I'm seeing an awful lot of biased opinions coming out. I'm not saying that 1x9 barrels aren't junk, apparently they are. But I would never make a claim saying that they are completely useless either.

    I remember not so long ago that the military used 1x11 twist rates in all of their barrels. I seem to remember them doing a lot of killing back then.



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